<edited because I was told to>
The vicious, but largely unconfirmed rumor is that WOTC intends to move D20 Modern to it's streamlined system from 4e/Saga.
Since this isn't even on their release schedule (or I've missed it) I've got LOADS of time to speculate how they'll do it.
Combat works the same way that 4e does. Attacks are made against defenses. Your attack is done as 1/2 level +stat mod +circumstance modifiers (weapon bonus, magic, feats, etc). Fort/Ref/Will modifiers are as follows
Strong +1 Fort / +1 Ref
Fast +2 Ref
Tough +2 Fort
Smart +1 Ref / +1 Will
Dedicated +2 Will
Charismatic +1 Fort / +1 Ref
HP will be CON+
Strong 12 +5/lvl
Fast 12 +5/lvl
Tough 15 +6/lvl
Smart 10 +5/lvl
Dedicated 12 +5/lvl
Charismatic 12 +5/lvl
The existing tiers from D20 Modern won't be used, nor will the ones from 4e be used exactly. It will be a hybrid.
Basic is 1st -5th
Advanced is 6th-10th
Paragon is 11th-20th
Epic is 21st-30th
In D20 modern, advanced classes were purely optional. In order to make this better fit the framework, they're required.
The skill list would have to expand a bit. Things like repair and craft would likely be rolled into single skills (Mechanics (INT) and Electronics (INT)). Craft Chemical would be handled as a feat ala alchemy from Adventurers Vault.
Backgrounds: Occupations are now your backgrounds. That feature was already pretty consistent with both games.
Feats: All (human) characters start with 2 feats plus any they may get from their occupation. Non human characters start with 1
talents: Human characters begin with 2 at will powers at 1st level and gain an additional at will when they take an advanced class. Non human characters start with 1 and gain the additional when they take an advanced class.
Progression (at this point) is going to look something like this
Basic
Level Stat Increase Feats Talents At will Encounter Daily
1 - 2 2 1 1
2 - 3 2 2 1
3 - 3 2 2 1
4 +1 to two 4 2 2 1
5 - 4 2 2 2
Advanced
6 - 5 3 3 3
7 - 5 3 4 3
8 +1 to two 6 3 4 3
9 - 6 3 4 4
10 - 7 3 5 4
I envision talents as being a mix of utility and attack powers. For Example:
Talents draft:
Strong Hero
At-Will Talents
Put in the effort
Strong At-Will Basic
You push yourself to new heights
At-will
Standard Action Personal
Effect: You make a strength check or strength skill check. You gain a +2 to the roll.
Board Breaker
Strong At-Will Basic
You can find weakness in objects and smash them to pieces
At-Will ✦ Martial,Weapon
Standard Action Melee weapon
Target: One object
Attack: Strength +2 vs. FORT
Hit: 1[W] + Strength modifier damage.
Increase damage to 2[W] + Strength modifier at 21st level
Melee Smash
Strong At-Will Basic
Your attacks hurt, a lot
At-Will ✦ Martial,Weapon
Standard Action Melee weapon
Target: One target
Attack: Strength vs. AC
Hit: 1[W] + Strength modifier damage +2
Increase damage to 2[W] + Strength modifier +1 at 21st level
Encounter Talents
Climb that mountain
Strong Encounter Basic
Few things stand in your way
encounter
Standard Action Personal
Effect: You make a strength check or strength skill check. You gain a +4 to the roll.
Wall Smasher
Strong Encounter Basic
You can bring down large obstacles with a mighty swing
Encounter ✦ Martial,Weapon
Standard Action Melee weapon
Target: One object
Attack: Strength +4 vs. FORT
Hit: 2[W] + Strength modifier damage.
Melee Crush
Strong Encounter Basic
Your attacks leave opponents reeling
Encounter ✦ Martial,Weapon
Standard Action Melee weapon
Target: One target
Attack: Strength vs. AC
Hit: 1[W] + Strength modifier damage +2 and the target is dazed until the start of your next turn
Daily Talents
Unstoppable Fitness
Strong Daily Basic
Nothing stands in your way
Daily
Standard Action Personal
Effect: You make a strength check or strength skill check. You gain a +6 to the roll.
Rock Crusher
Strong Daily Basic
You can bring low the strongest obstacles
Daily ✦ Martial,Weapon
Standard Action Melee weapon
Target: One object
Attack: Strength +6 vs. FORT
Hit: 3[W] + Strength modifier damage.
Hulk Smash!
Strong Daily Basic
Your attacks leave opponents reeling
Daily ✦ Martial,Weapon
Standard Action Melee weapon
Target: One target
Attack: Strength vs. AC
Hit: 2[W] + Strength modifier damage +2 and the target is dazed until the end of your next turn
On skills
Number of Skills per basic class:
Strong: 4
Fast: 6
Tough: 4
Smart: 9
Dedicated: 6
Charismatic: 6
Half-thought out skill list
Acrobatics (Dex)
Arcana (Int)
Athletics (Str)
Bluff (Cha)
Computer Use (Int)
Diplomacy (Cha)
Drive (Dex)
Electronics (Craft and repair) (Int)
Endurance (Con)
History (Int)
Insight (Wis)
Intimidate (Cha)
Mechanics (Int)
Nature (Wis)
Perception (Wis)
Perform ** Waiting to see if PHB2 covers this **
Pilot (Dex)
Religion (Int)
Stealth (Dex)
Streetwise (Cha)
Technology (Knowl)
Thievery (Dex)
Treat Injury (Heal) (Wis)
Couple of feats to handle unarmed brawler types
Fisticuffs!
Your hands, feet, elbows? Lethal weapons
Effect: You are proficient enough with your unarmed attacks that they no longer are considered improvised weapons and gain a proficiency bonus of +2. Unarmed attacks for medium sized creatures do 1d6 dmg
Fists of Fury
You've watched every bruce lee movie, twice
Prequisites: Fisticuffs
Effect: Your unarmed attacks do 1d8 damage