Unless there's a reason that makes changing systems extremely compelling, I usually rather stick with the current system and buy a newer version of whatever I'm using. Switching systems can be very expensive especially if you already have an existing collection of lenses. Personally a few years back I considered switching to Sony from Canon because of the A7SII's high ISO performance for video, but I held off and bought a Sony camcorder instead while still keeping my Canon gear, mainly because selling off all my Canon gear and buying Sony / Zeiss equivalents costed way too much.
That being said, if you have the budget and have found a specific feature another system offers over your current, don't be afraid to rent some equipment and try it out before you decide to buy.
On a wholly unrelated note, I've reached 100 posts with this post!