This is a big business move to get all the zillions of graphics, editing, advertising creative departments, effects houses, designers, larger photo studios, retouching houses, etc. on a steady income generating stream for Adobe rather than a once in a while upgrade path that any company could skip in down times. The regular pro photographer and advanced amateur are a drop in the bucket in comparison.
For the latter it creates a very uncertain future in a category already beleaguered with uncertainty.
"What? They have no bread? Then let them eat cake!
"What? They have no Photoshop? Then let them use Lightroom"
IMO and direct expereince, the strength of Lightroom is its synergistic link to Photoshop as an "Open In" option, providing quick access to deeper retouching tools, layers, and layered plug-ins such as Nik software like Silver Efex Pro-2. (Nik was purchased by Google, who instantly made all the Nik plug-ins suites available for a modest price, but created uncertainty as to what the future held for Nik software direction.)
I also use OnOne Photo Tools that is a layered effects suite plug-in under "Automate" in PS.
Without PS, these software solutions are not applied as layers, (i.e., Nik Silver Efex Pro-2 stand-alone is not a layered file).
Any of these solutions done in PS were then returned to the Lightroom library as a version, thus completing the workflow circle intact.
As it is, I can live with PS6 as long as it can update RAW compatibility for new cameras, and is compatible with the newer versions of LR (because I NEVER use Bridge/ARC to process RAW files). Adobe says it will allow PS6 users to acquire the later versions of ACR but will not allow use of any new features in later versions of PS. We'll see how long that lasts, since I do not believe them longer term.
IMO, anyone running PS 5.5 had better think about updating to PS6 while you can, since Abobe will not be making new versions of ACR available ... for example, and correct me if I am wrong, the Nikon D600 RAW files require the latest ACR 7 version which isn't available for PS 5.5. This isn't meant to further support Adobe, but to buy PS users some time.
Those who use the more extensive PS Suite, including In Design are screwed unless the current version lasts a while. However, Quark was a lesson in horrid compatibility with previous versions, and this move smells the same.
-Marc