Heads-up, I think the stream Capcom TV did today confirmed Extreme Battle Mode.
There was a new song from REmake 2 playing in the background of them talking in the stream. This was the clearest time stamp I could find where you can hear it (2 hours 6 minutes and 40 seconds in):
I recognized it but couldn't place on where I'd heard it before, so I quickly went through all of RE2's music and I think I found it.
It's a bit hard to hear, but I think it's a new take on the Extreme Battle Mode music from RE2:
So if I'm hearing it right, I think it might confirm Extreme Battle Mode is in. There's a few songs for Extreme Battle Mode, but all of them use a few similar sounds to each other not used in the rest of RE2, and the song from the stream is using those same sounds (the drums, both the bigger and more military ones, this one low horn thing, and a few other touches), so I'm pretty certain even if not the exact song it's an Extreme Battle Mode song.