No, not automatically but some will and some won't with a paperwork exercise. It depends on whether the same airframe has been approved under Section S and flown at higher weights e.g. EV97 Eurostar is rated at 480kg as a "Fixed wing land plane" so the microlight upgrade should be a paper exercise supported by the manufacturer/importing agent.
Same applies to any approved for 472.5kg with a BRS should be able to go to 472.5kg without.
The C42 B/C is a likely candidate for the paper upgrade as the same airframe is already tested to 540/560 by the manufacturer. Model A may be only 500kg.
Other and older airframes such as X Air or Thruster etc will not be very likely to be rated higher due to the cost of testing required by the manufacturer with no benefit to themselves.
The Skyranger looks to be an early contender as the Swift 2 and Nynja have been built with the higher MTOM in mind.
Disclaimer, this is what I've gathered from some in the know. Happy to be corrected. It'll all come out in the wash.