Interesting, my friend, but perhaps a little overstated? What I mean is that, this would be somewhat analogous to saying:

"Writers Create a Completely New, Never Seen Before Shakespeare" and then explaining that these "writers" have replaced all instances of "you" with "y'all" instead. Romeo and Juliet would still be readable, but with a slight southern accent... ;)

"But Romesberg says there's no need for concern just yet, because for one, the synthetic base pair is useless. It can't be read and processed into something of value by the bacteria"

Indeed... We do know a lot more about life than we did when I was a boy, but mostly what we have learned is that it is incredibly complex and not susceptible to easy re-design.

After reading your source article, the achievement seems to boil down to having figured out how to insert a couple of "new letters" into the alphabet without killing the original organism.

I don't mean to minimize the usefulness of this - but for the moment, my sense is that it could be a way to encode and store information into living and replicating organisms for posterity. Sort of like the Steemit blockchain has properties that may enable archiving data for posterity.