Will a GPU be required to do proof of stake as a full node? Will it help me be more profitable? Will a highly available network connection be worth more than having a beefy GPU? What if I don't stay up for the 4 month period? (What sort of reduction in my money will I see?)
Many details remain, however most PoS implementations require only that the software is running for it to vote, and very little or no computation. A hybrid system could be used, but there is no clear evidence that a GPU will be required or beneficial for Ethereum's Proof-of-Stake algorithm, Casper.