Upgrade late 2008 15" MacBook Pro with newer logic board?

I'm gonna venture a guess and say no.

Everything is packed in so tight with laptops in general and this series in particular that any change under the hood will produce another logic board shape.

You're in luck though, because the shell hasn't changed yet so feel free to buy the best Apple has to offer new (with all those extra wads of cash that are lying around all over the place...)

Every model of the Macbook Pro has a differently shaped logic board. Usually the fan location and the location of the ports is changed, making it near impossible to put a newer logic board in an older unibody casing.