OK. You have no hard numbers, and that's fine. Most people don't. What are you basing this analysis on, then? Honestly, I would love the reassurance. My read as an armchair analyst is that it'll be a small miracle if Year 3 stuff gets the green light. I'd love to understand why you are so optimistic.
Year 3 already has the green light. If it goes beyond THAT, well, that's anyone's guess. But the amount of lead time WB needs to secure IPs, then Lego needs to actually make the custom parts and design the sets, let alone the time they need to give Tt to create the game content, means that when Year 1 was coming out they were designing Year 3 stuff already. They definitely had some kind of roadmap of IPs and release dates planned, at the very least:
"We have a three year plan at the moment and we've got no intention of stopping there," associate producer Mark Warburton told Eurogamer during an interview conducted at EGX.
I personally don't see it going beyond Year 3, though I'd welcome the surprise. But I
would be surprised if they ended it before Year 3 came out. That would be Summer 2017. I don't know much about how long it actually takes to make the levels or adventure hubs or battle arenas, but let's say it's 6 months (which I feel is ridiculously short but again I know little about this part of it and I'm just using it for the sake of an example). That means that if Year 3 comes out in September 2017 (Year One was Sept 2015 and Year Two was Sept 2016) they'd start working on the levels in April of next year. Which means that as of April of next year they'd also need to have the licenses ready and the toy designs finalized and ready to start mass production.
Source: I worked for Lego for a couple years so I've heard here and there about how far in advance they plan stuff. For example I think I heard about the DC Superhero Friends sets about a year before they were revealed? I knew about the Green Lantern set they showed off at SDCC at least 6 months before it was revealed too. In the Lego OT we usually see leaks of temp box arts at least 3-4 months before they're officially shown off, let alone go on sale. Think about how far in advance we start hearing rumors about stuff like future versions of iPhones etc and you'll get a general idea on the lead time to bring something to market - obviously a Lego set isn't as complex as an iPhone but the license + physical toys + video game does still take some time to design, create, and bring to market, also taking into consideration the production pipeline for all the other stuff they're making. They're most likely gearing up to start production on Year 3 stuff right now (if they haven't already) even though we won't hear about it until around E3 in June.
I wonder if they have some metric or way of comparing how a Dimensions Story Pack sells VS a standalone Lego game. You and I probably expected Lego Batman Movie The Game and Lego Fantastic Beasts The Game, yet those got Story Packs in Dimensions instead. So the $50 Story Pack plus the cost of the literal and figurative Dimensions Gateway to play it VS a stand-alone $60 game, I wonder which one winds up being more profitable for Lego?