If they burn their 80% stake, crypti can still go on.
I wondered if they might burn some of their coins, but then realized... what benefit would it be to them?
They burn their coins, XCR rises in price... but they won't benefit, as they burned their coins. XCR would then be deemed a competitor to Lisk.
If they hold their coins, they could do several things. First, just let XCR die. It's a competitor in a way, so that's an indirect benefit.
They sell half to a dev who wants to take over XCR. It's an insane amount for two parties to hold in a coin, but it could result in at least sustaining things for a while. Then they can sell small amounts over a long period of time. XCR would never truly succeed however, as it's like never-ending sell pressure (if not from the Lisk devs, then the new XCR dev).
They just sell what they can, hold onto what they have... if XCR lives, they do the never-ending sell pressure thing and just get what they can out of it.
There are several possible scenarios, but not very many that make sense for the Lisk devs that also results in XCR succeeding longterm. In fact, I see no logical reason for them to do anything with their XCR besides sell what they can of it. Maybe a whale or two would pay them pennies on the dollar for their XCR, then whales use the XCR as a pump mechanism ... but again, that's not healthy for the coin longterm.