Sounds like poor optimization or coding than actual hardware limitation. The cell processor is notoriously difficult to code for but the series you mentioned is hardly ground breaking in terms of visual technique.
In any case, I doubt we'll see the median of new console performance until the 2nd or 3rd reiteration. By all report, the new system is supposed to be a lot easier to use than the power pc architecture of last gen.
Also, MS bought out the Gears of War license from Epic and Black Tusk studio is assigned to it.
(source). Kinda shitty considering the initial announcement that Black Tusk was going to work on a new IP but in terms of business sense, it's the correct decision. Gears is still an hot franchise and there were rumors that Epic wasn't going to stay exclusive with Microsoft. Securing an established franchise and having Black Tusk develop it instead of a brand new IP is a lot less risky.
Still, kinda shitty nonetheless since new IPs are always exciting to see.