I have a 2017 orbea rallon with 27,5 wheels. I have been given opportunity to get Nice forks, but should i get 29 forks to use with my 27,5 wheel ?
Just in case i want to change the frame next year.

Will lift the front of your bike by an inch or more, which will be bad for lots of reasons (unless you get shorter travel 29er forks – say 130mm instead of 150mm)

Check the Axle-to-Crown measurement of your current forks vs the new forks…. 20mm difference will change the head angle by approx 1 degree (simple math), as well as raising/lowering the BB.

As above. I did this when I had a Cotic Rocket with 26″ 150mm forks. I knew I planned on getting a 650b bike in the future so upgraded to 130mm 27.5″ forks with the 26″ wheels in.

Joke was on me though: I ended up going 29er so had to sell the forks after all.

I tried it on a Whyte G170, it was horrific

Thanks all, going to stick with 27,5.

IME, a 51mm offset 29″ fork feels AWFUL on a 27.5″ bike. Even if you match the Axle to crown measurement.
However a short offset 29er fork might feel OK, if you get the A-C close.

If you’re on a small frame you may get toe-overlap issues.

The flip side is that I ran 140mm + 150mm forks on my Orange Segment which was designed for 120mm and it was fine.