But why? Why just consider switching? Why not wait to see what, if anything, actually changes? And if those changes are for the better? You had a valid reason switching from Wordpress to Tumblr, but you don't provide one from switching away.
There is so much angst from the teenage users using Tumblr that are panicking about the buyout and making similar threats. I don't expect to see that mentality without sound reasoning on HN.