Re: Here's a thought...
There's nothing to fall back on with the Nexus 6.
There's nothing to fall back on with any phone running Lollipop, not just the Nexus 6. That means all the Moto Xs (2014), Moto Gs (2014), LG G3s, NVIDIA SHIELD Tablets, etc. etc. already running Lollipop are in the same situation.
Most manufacturers are targeting before the end of the year/first months of next year to update their newest/most popular phones to Lollipop. Lollipop is the future and this pretty much forces the developers to update their applications or get left behind... It's definitely a good thing.
I'd rather everybody push forward than to stay behind, which is also why Motorola (remaining phones), Sony, Samsung, HTC, OnePlus, are getting their updates ready ASAP too.