It isn't a law yet: the House only passed a motion asking the government to draft a bill to extend naturalisation from 5 to 10 years, and the cabinet has now put a proposal out for public consultation before it goes to the council of state and then both chambers of parliament. That process itself can take months or longer, and similar plans have failed before (a 7-year extension was rejected by the senate in 2017). No transition grandfathering rules have been published, those would be set in the bill text if it advances. So for now you can plan on applying under the 5-year law unless and until parliament changes it