I don't see extensions being a priority in the immediate term. The eastern and western extension of the planned LRT would be pretty low ridership additions and honestly make more sense as bus connections anyway.
The next-best corridor for LRT is James up the mountain, which will be a hugely expensive line as you'll have to tunnel up the escarpment most likely. I would love to see a connection from West Harbour up to Mohawk College then to Limeridge as the next LRT phase, but that's going to be a long ways off still.
I think the extension makes sense into Dundas given it's a moderately dense area and is fairly short. Stoney Creek is less so as it's just more mid-century sprawl with no clear anchor. Worth factoring in is the notion of 'deservingness' on a smaller scale akin to what happens in Toronto (Scarborough deserves X, Etobicoke deserves Y). Dundas is one of these post-amalgamation communities with a long history and sense of identity, which might pull some weight in getting the LRT there. It also might help sort out the mess of buses in Dundas.
The A Line has gone through various iterations and is always thrown back and forth on what it will be. The now-scrapped branch would've just gone from King to West Harbour via James st, which would be fairly limited in its utility but would have set in stone the decision to use LRT instead of BRT. I don't prefer the latter because I don't see it bringing the development needed to Upper James, is less attractive to potential riders generally, and (imo) wouldn't be enough capacity by the time we actually get around to building it. There are a variety of key ridership nodes along its length justifying higher-order connections, more than the B Line I'd argue. An LRT would also bring rail access to the mountain again after nearly a century of no such service.
There are two options for an A Line LRT; either travel at-grade up the mountain via Wellington/Claremont access (already studied), or tunnel it from James to Mohawk College and continue at-grade from Fennell to Upper James all the way to YHM. Using Wellington misses much of the potential trip generators along James st, while tunnelling would be cost-prohibitive. At that point, it is worth at least considering grade-separating more of the line, which is fantastical, but was at one point proposed as part of an ICTS system to Limeridge from a downtown loop. Given its ambiguous inclusion again in the GGH 2051 plan, I do think LRT will be considered but pushed very far down the timeline, unfortunately.