What's next after lunges?

Heavier lunges? Full squats back and front? Just mix it up? What are people doing or planning?

That's a good question. I'd personally look at dynamic exercises and by the time I get there, Movement will most likely be released. So that's my plan. 

Until the release, it'll probably be up to each individual's goals. I'll certainly have to work on my back squats at some point as I want to beat my dad's record. 

I'll be leaping over tall buildings.

I'm going to keep doing them at 5x5 for a few weeks then do one session as full squats and one session lunges in a month or two. Then rotate in front squats and slowly get back into olympic lifting so long as the other foundation movements are slowly moving forward.

I'm going to add steps to the lunges from this week; I have a long strip of grass at the back and one way is more like 15-20 steps than the 10 I've been doing

And about the weighted arc up? Just hold more plates as a progression?