Hence the "why do it now?".EugW wrote: ↑First off you should choose the wall where you expect to need it, but I understand plans can change. However, you can get conduit and run it along the baseboard. The plastic conduit isn't exactly bargain basement cheap, but it's not that expensive either and it's extremely easy install. The smallest wiremold is about 1 cm tall, enough for a couple of Ethernet cables.
As you said: It's easy
So there is absolutely no reason to do it pre-emptively. You'll only be working 5x more because odds are that you won't use more than 1/5th of those jacks if you wire up every room.
Wait until a need comes up: Wire things based on the need.
If anything, the only pre-emptive expense is a 1000' spool of Cat6, a crimper, and a bag of 100 jacks and plugs.