Another new Beach Boys album seems likely(whether it's some of the 16 outtakes from "That's Why God Made The Radio", or all all-new effort) and there would likely be some tour dates to promote it, but after that, Melinda & the other people surrounding Brian should finally let Brian go back to being a studio-only artist. For Brian's handlers, he's the goose who lays golden records, but it wouldn't be good for Brian's career to conclude as a touring performer singing from a wheelchair.
From cabinessence.net:
"I can tell you the day the Beach Boys will no longer exist--never. We'll be on stage in wheelchairs."
..................................Dennis Wilson, 1977