I got this text yesterday, too. I wondered how long it would continue for. Not sure what I'm going to do yet. I'm one of these people who don't text or call very much, so the unlimited TXTs don't mean much to me. Having more data is good, but the Spotify was key for me being that I lost hundreds of CDs in a fire a few years back and just had no way to go and buy it all again.
So I just use Alexa to bring it up now. I agree with the OP that it is probably more advantageous to Spark than for those of us who were on the plan.