If you can't afford to lose your money without making any ROI though, maybe you should think again.
If it goes POS, there is going to be millions of idle GPUs out there which will be scrambling to mine any decent coin at all. The difficulty will skyrocket and only those with near free power will be able to mine it, most retail people won't be able too. It will be game over. You can't mine coins like Litecoin or Bitcoin with GPUs anymore.
Yes you can sell it but depending on how much you pay now, and what new models come out in the future its hard to say how much you will get for it. Gamers which buy our GPUs are smart. If they find out that ETH is POS, they know they can score a deal and you lowball the hell out of miners. And some miners might cave and sell their GPUs for like 50% off their buying price, which can be >$500 in some situations.