i doubt there are fpga for x13 already, come on it would be insane..., the x13 mania just started two days ago
one 280x can do 2.5M on x13, reaching 50 giga with those cards is not that crazy as you think
50 giga are like 20k 280x, 200 big farmers with 100 cards each is quite easy to achieve
the real problem are those big farms, that keeps adding gpu because they can make roi for each new rig very fast
I'm 99.99% sure there are bitstreams for FPGA's already (not ASICs!) as there were already some for X11.. X13 is nothing more than
X11 plus two algo's, MaruCoin is quite old already, so the devs had plenty of time rewriting the bistream.