Curiously out of date...
Guys, this article and some of the comments are a little misinformed.
Microsoft adopted a 'cloud-first' policy across the company several years ago (back in the days of Ballmer). This is now deeply baked into the technology and product roadmaps. Product groups across the company are required to put cloud services, including Azure, at the centre of their plans and the investments they make. This is old news, and applies as much to their efforts in the integration space as anything else. The 'cloud' dog has been wagging the Microsoft tail for a long time now.
Yes, there is lots of BizTalk stuff going on behind the scenes which Microsoft will announce in detail when they are good and ready. Yes, the aim of 'symmetry' is strongly in evidence, and yes, the cadence across all of Azure, including BizTalk Services is far more frequent than for on-premises server products. It has been for several years now.
BizTalk Services, which is currently at a very basic version 1.0 stage, is a PaaS offering. The central value proposition of PaaS is that the service provider (Microsoft, in this case) controls the stack all the way up to and including the run-time environment (the code container), including patching. That includes the networking, hardware, virtualisation, Guest OSs, middleware, etc., as dogged has pointed out in his comment. This is a very, very different model to on-premises, co-lo or even managed service hosting used for products like BizTalk Server. BizTalk Server therefore continues to have a much slower cadence of releases. Hybrid-ness is vital in this new world, and if you look carefully at what Microsoft is doing publically on Azure today, you can spot some of the ways that future releases of BizTalk Services will support the hybrid model. Can't go into any more detail 'cos of NDA, but watch this space. I will say that the BizTalk world is certainly feeling some heat at present from some of the light-weight cloud-based integration options out there, and this will be responded to comprehensively in due course.