Yes, there is likely to be some impact, mostly on the 'Editing Simple lesson' page. (I am looking at the screen-grabs on the plugins DB entry.)
The part where the teacher wants to pick a question from the question bank to add to the lesson will need to be updated (in a way similar to how the equivalent part of mod_quiz is changed - so, when the time comes for you do to this, there will be some example code to look at).
It has been quite viable for other activities to use questions from the question bank for many years. Some activities have done that and are in the plugins DB (e.g. mod_studentquiz, mod_adaptivequiz, mod_offlinequiz, ...)
Lesson has never been converted. MDL-18954 has been there for a long time! As Richard says, how to make branching work is the main issue. (Not impossible to imagine a solution, but might need some additions to the core question system to make it work really well.) Anyway, until someone decides they are up to the challenge of working on it, then not much point discussing the details.
Hopefully it will be less alarming as you learn more. This is nothing new. These are exactly the same changes we have been banging on about for years. Most recently here. The plan has not really changed, it is just taking a long time to get finished, but, hopefully, we are getting close now.
Quite a lot has not changed in this latest installment. Things that stay the same:
The changes are:
Linked to the tracker issue, there is a prototype site where you can try out the mostly finished code: https://sharedquestionbanks.prototype.moodledemo.net/ you can log in as t1 or s1, both with password 'moodle'. (That is, teacher and student.)
(Thanks to Mary for splitting off this thread. I think this part of the conversation is much more on-topic here.)