I got a road bike 3 years ago to train for a triathlon, about a year later sold my Trek Fuel frame, and built up a very nice 456. sold it 6 months later having ridden it once, or maybe twice. I’m a fully fledged roadie now, 250km a week, love it.
BUT, recently I have been thinking about an MTB race bike, maybe a boardman on C2W, just to see how fast I’d be after 3 years without an MTB.
The way I look at it, I’ll always have diffeent bikes, and be into different types of riding at different times, if you do go all roadie, and decide you don’t like it, it’s easy enough to go back to MTB