GM only went with a 302 because they were limited to 5.0L and the small bore 307 was not up to par, not that they thought a smaller motor was better.
I don't see a turbo V6 on a high end offering. It's cheaper to offer a standard V8 that shares most of it's build with every truck engine they have, Ford uses the ecoboost 6ixers in lower scale offerings not their upscale trucks stangs etc. It does not equal their 5.0. I don't see GM doing anything different rather than improve what they have which has been working great so far.
Unless they manufacture a whole new V8 engine a 305 CI engine that is just as large, heavy, and as expensive as a 6.2 wouldn't make much sense. All LS engines reguardless of Cubic inch, are physically the same size. Why give up the cubes and low end torque when the rest of the engine is identical to the bigger ones? GM's 4.8's (the closest thing they have to a 305) aren't exactly the same league as the old school 302's and are way outclassed by their bigger brethren, and I'd wager that the 302's heads and cam and intake would have done alot more on the 350's.
Ford uses smaller CI motors due to the complexity of the DOHC designs, they don't have much choice. Their 6.2L DOHC engine is huge and heavy and wouldn't fit under the hood of a stang so that's why they are using smaller CI but physically larger, heavier, more complex motors. GM is using the KISS method saving money, weight, complexity and using larger CI but just as, if not more efficient, engines. Take the 6.2 Vs 5.0 comparo on MPG. The MPG numbers listed for the 5.0 are using lower (numerically) gears than whats in the SS (not the track pack or 3.55 geared stangs), weigh less and I'd argue are a tad more aero, with the smaller frontal area, yet only gain 1-2 MPG difference. That shows me the lower CI, DOHC with all the fancy doodads arent as efficient as a honking 6.2L that is lighter, smaller physically, cheaper to manufacture, with less crazy stuff on it. If the current Camaro is on the heavy side imagine what 3 more cams, wider block and heads, 4 times the length timing chain and all the other sensors etc for a smaller dohc V8 would do. On the turbo 6 side all the extra plumbing isn't saving that much on weight as well.
The rumored 5.5 is going down cube wise probably for the same reason to make room for all the other high tech gagetry needing to take up room in the block.
If size was a concern I'd go with a boosted six but since it's not, no thanks. Boosted means forged internals (more money), more parts to contend with, more warranty issues, more chance of bad gas screwing something up, which all add up to more cost than a simple V8 that works just as good. I applaud them. So far I see no reason to switch to a DOHC to sacrifice cubes. My 2 cents worth
2000 Red 1SC Z28 A4 - dead for now
2005 Black GTO M6 6.0 - Split daily driver
1987 Silver Fiero GT - Split daily driver