I have a couple custom modules but nothing tricky or particularly oriented towards rendering.
I expect 3.4 will maintain backwards compatibility WRT to class names so porting my modules would only require recompiling.
I've been using the sql-lite plugin as well and don't know if support has been integrated (differently)
I am running on a mac air (2015) Mojave so I worry a little about upgrading.
Any caveats are welcome!