I think they'll continue, because just having a video "assembly" at the kingdom hall/assembly hall (at least in the combination buildings I've seen in the past) is nothing special. Just like being at the meeting, only longer. The bOrg probably knows that the sheeples need something special to look forward to (ugh) and the assemblies kinda provide that. And, if you're single and a good little dub (no online dating allowed for you!) there really isn't anywhere else to meet anyone unless you're special enough to be on a KH build, or whatever the special privilege du jour happens to be.
But without the excitement of a new book release it is tricky. People in general don't spend unless they have something tangible in hand to connect it to.
But, going to all one and two day only assemblies in the future? Maybe.