:::::Yes, thank you. Celts (modern) is superior to "Modern Celts", because the "modern" is not part of a proper name, it is just an adjective used for disambiguation from the Celts of antiquity.  
 :::::However, Celts (modern)  will still need to be disambiguated, as the term may either refer objectively the million or so Celtic speakers of current times, or then again to some political or ideological notion of a "Celtic nation" or "Celtic ethnic essence", probably best termed Celtic identity. Merging with Celtic nations is fine, too. Modern Celts can redirect to Celts (modern), and Celts (modern) can be a disambiguation page for extreme clarity.