Well you'll have to switch wheels too. 26 x 1.95 is a ISO 26 x 559. So you can only use tires that have a 559 BSD. 27.5 tires are ISO nn x 584. The bead seat diameter will be too big and they'll not even touch your current wheel rims.

If you switch wheels, you'll have to worry about frame clearances and finding hubs that'll work with your disc.