I think they should buff him and i expect them to. Right now D.Va has jacked the dive slot. She can initiate and re-initiate quicker, Its far easier to survive while doing it (her K
rate on PC is pretty good, on consoles its downright insane), and she does more damage. The only pro winston has over her is aoe damage and it goes through shields.
If I were to buff him, i'd focus on the shield so he can initiate and re-initiate quicker. I'd like to see it take more damage but the cool down is the key. At a whopping 13 seconds its really only there to buy a second or two for the jump refresh in a emergency situation or to secure a kill. Maybe back in the day when you could have 6 winstons dropping bubbles all over the place that might have been ok, but now it just doesn't make sense. It doesn't provide that big of a benefit to be so damn rare.