Fgo to end after Arc2?

As much as I know, despite many disscussions have been made, it is known that Nasu will take a break from involving with FGO story and quality checking to work on other projects. The game itself is written not only by himself, but other authors as well. If anything, FGO Jp won 2nd prize as being the second populous game (money making) and raked up billions for Sony Entertainment. It would suprise me very much if they decided to put a stop to the golden chicken like FGO just because the main author is going to take a break (maybe he is just tired and cant think of something new).
That's all I can say...Part 2 is not done yet, so we will have around 3 years of content in the future for NA :) Just enjoy the game for now!

Don't worry at all about the game "ending" tbh. Nasu will be leaving and wrapping up what he sees as the "Grand Order" storyline but that doesn't mean there can't/won't be other stories taken over by the other authors of the game. Expect something Epic of Remnant style in the year after part 2 concludes and then I guarantee we see a part 3 which takes the game in a new direction, possibly with a new protagonist which many have speculated.

As mentioned above, one of the largest factors when deciding whether to keep an online game like this alive is the funding and the profitability. FGO has massive amounts of funding thanks to all the whales in the game and the quartz sales have doubled in just the last year. This game will live so long as there's money to be reaped from it.

Just the story not the game. I mean some people play for gameplay, waifu,... not for the story

As the others have said the game rakes in too much money for them to just drop it all the sudden, even if Nasu’s Leaving, they’ll likely just get other writers in instead. Plus as you said it’d be weird for them to announce this news if they were planning on ending the game because players like your self would stop spending on it and when it comes to making money I doubt they’d be that dumb.
Though it would be nice for them to give some idea of what their plans are for after lost belt, since it would help put at ease some of the more worried players.

It's seems true that he will take a break from FGO for a while. He stated that it would be difficult to write what happens "after the end", its mean he doesn't have any story to write after arc 2. So it make sense to him left this game.
.IMO, same as fgo story, as long as player and historical figure that can be used to make a new servant still exist, this game never meet the end and will continue to the future (except the developer try to send grail to the future and decide to end the game)
Just kidding..

No no, it's just that Nasu is leaving Fate in the hands of another trusted director so that he can work on other projects

There was a big discussion on reddit about this. While in general, it would seem unlikely for such a money maker to end, there were comments on reddit that unlike most games, Sony and co gave Nasu total control over the game, including the ability to end it. While I'm sure they would prefer it continue, it might depend on how much Nasu will rest on his "artistic" reasons for ending it, and/or whether he might be bought out if he doesn't want to work on it anymore.

But putting out a story like this must irk the companies involved, as spending on digital assets that could go poof like that would really shake the business model funding it.