It's depends u actually...
Yes GPU is always upgrade to newer again after a year, but how we to be able to chase?
If u are not a true gamer, this GPU is already enough for u

Actually my friend also looking for lollipop chainsaw, but I still no see any news abt it

The thing about SLi is that, you pay nearly x2 but you manage to utilize 1.3-1.8x only

This is especially medium to low range GPU as GT750M. Sound very cool, yes, but not really money-wise for me.
You better go with single, strong GPU instead of 2 average GPU. At least with single GPU, you may squeeze all the juice needed from a sole source.

Not recommended to OC due to heat and stability; and the juiced gain from the OC not not so much. At best you can gain 20%, from my approximation.

To be honest, few people that own your laptop saying to book RE-15 once they sell that Lenovo for better and more stable GPU.

Averagely speaking, this is true since GTX770M and/or GTX760M are most likely to use MXM, hence it is upgradable in future.