I don't feel much of a surprise on hearing this, it makes a lot of sense if HTC decides to abandon it, apparently almost all their development are focusing on Android devices, yet still yields a extremely poor market share.
Also I heard some source indicating HTC would still intend to develop a Win10 Mobile device, for that I won't be of any surprise, since HTC still develop windows devices to this day, and still not officially announce that they would totally abandon Windows phone OS, that leaves some possibilities for future Win10 mobile devices from HTC. Still since this is unconfirmed, I shall take it as rumor.........