The makeup of this group makes them vastly more credible than Mikin 'red-list' Hearndresen and the Bitcoin Foundation circle-jerkers.  I would absolutely consider their work on Bitcoin to be the mainline branch and TBF-associated 'enhancements' to be a side-branch if/when push came to shove.  And very possibly a hostile side-branch.  Hopefully the big miners are clued in and still independent enough to see things the same way.

If Peter Todd came up with a workable generic shared ledger, especially one which employed treechain methods, I'd consider it a (very interesting) alt-ish type thing.