I think Lajoie & Lagha will get a host spot.
(It's possible there could be a bit of a fight over that if Canada chooses to invite two top teams to SC and then has to choose between S&F and L&L. All three of the top Canadian teams are high enough on the SB list that they are highly likely to get two non-host spots even if F-B&S miss the top ten at Worlds, which they have a good chance of making).
Then if L&L don't make the WS top 24 or SB list, there might be some wrangling on their behalf for a second, as Canada has invites to trade.
If they are still not top 24 on one of the lists, they would need to win JW to get a guaranteed GP spot (other than a host pick, of course).
You can't get a guaranteed spot by winning Junior Worlds. (At least you haven't been able to do so for several years. If that has changed, I would love a link to the information).
A win or a medal at Junior Worlds, though, would give L&L a lot of WS points. I think once scores were dropped for the transition to next season, they would have a chance of making the top 24 if they bring in those points.
They could possibly earn a top 24 SB score at Junior Worlds, but that is hard to do with the fewer elements that junior teams have. (Ushakova & Nekrasov and Shevchenko & Eremenko currently have scores on the list so reaching #22 and below is possible for the junior teams, maybe #21. I feel like #20 would likely be out of reach based on the junior scores we've seen thus far). Then you have to cross your fingers and hope the senior teams from Worlds don't spring past you. Earning a top 24 SB for L&L is not particularly likely, though it is common for JW scores in March to outpace JGP scores from months earlier.
Are they eligible for junior for another year anyway?
Yes, they have another year of junior eligibility.