Looks to me like "Season 4" is going to be a direct lead-in to Bloodgames 2. My guess is they enjoy rugpulls so much that they thought it'd be funny to rugpull a whole season. Bloodgames 1 was notoriously under-watched because people didn't know what it was, so the wiggers decided to build a little more hype with a goofy, half-assed Season 4 trailer. I'm sure they'd prefer to go into Season 5 after BG2 anyway, it's just a better number for a big season.
Will the first moments look like a regular season? Will the fish be real contestants or actors? How long will the season run before the switch? Should be fun.
As an aside, how many blurred people in the trailer have been identified at this point?