I've really been thinking about this.

Now that the GS will have upwards of 300 horsepower in base form, and damn close to 400 horsepower in the GS460, it seems logical that the IS will see a similar boost in trimlevels/horsepower.

Lexus seems to be jumping on the horsepower bandwagon. I truly believe the GS' upcoming boost is partially due to the fact that the Infiniti M is so powerful in base (M35) form. Now that the GS will outperform the Infiniti M in regards to horsepower, it seems logical that the IS will follow suit. The current G35 can be had with just under 300 horsepower for roughly the same price as a base 2.5-liter 204 horsepower IS. Ditching the 2.5 in favor of the more-powerful (but still not class-leading) 3.0 would bring the IS closer to the G's performance. The next-generation G35 will likely be even more powerful, and I'm sure Lexus hasn't let this very fact go unnoticed.

Maybe I'm beating a dead horse. But I can't give up hope in the return of an IS300. A base IS with 245 horsepower would allow it to compete with the competition more effectively. If the GS and other Lexus models are any indication, I firmly believe Lexus won't dissapoint. More importantly, if a more powerful base IS becomes available, I'll be the first in line.

 

I think that the if the IS needs more HP, it will create something not in between the 250 and 350, but more than the 350, such as the much much much rumored IS460/500. I doubt that Infiniti will make a V8 G (although Nissan will make the Skyline) to battle with a V8 IS.

If you're lucky, and you want something in the middle of the 250 and 350, perhaps they'll make a hybrid using the 250 engine. I think that if Lexus ever creates a hybrid, it will be more powerful than the 350, such as the 450h. Lexus hybrids (and the IS in general) are about more power, not gas efficiency.