Leon was my main in DOA4, so I wouldn't mind seeing him back.
One of the reasons you didn't see Leon often was the same reason you didn't often see Bayman or Bass or Brad in DOA4 - they were lower tier characters. I've seen a lot more Bayman, Bass, and Brad in DOA 5 online than I ever did in DOA 4 online, so I expect Leon might actually see some play time with new DOA 5 changes.
With that said, I would also be fine with not seeing him again, mostly because his japanese voice actor died after DOA 4, and I dunno if I'd have the heart to play him with a new voice actor. Tragedy seems to follow Leon everywhere.
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Ah geez, Leon.. TRAGICALLY MISUNDERSTOOD, THE UNDERDOG.. the WORLD'S STRONGEST MAN.... he really was a lover and a fighter. part rambo, part romeo, .. I'LL BUY HIM