Eh, I'd say about 30% or so. There are quite a lot of Nintendo fan projects like this that do fine for years; this one's been in public development for nearly a decade now.

However, there is a possibility that a fake take down might hit it. There have been stories about someone pretending to be a Nintendo lawyer and randomly taking down fan works, or maybe some sort of bot auto removing stuff under questionable premises.

For example:

https://www.youtube.com/watch?v=m_gnwn535eM

Or my post about the same matter:

https://gamingreinvented.com/nintendoarticles/fake-nintendo-...

However, it's not as likely to take it offline as for some projects. The imposter only seems to go after file hosts like Dropbox, Mediafire, etc. This fan game is also hosted on a Metroid fan site and isn't dependant on a company honouring questionable takedowns to cover their backside.

It might happen, but it could easily survive. Or have its mirror links taken down by an imposter.