LR5 can be purchased as a stand alone product, but to be honest, I think the writing is on the wall, and LR will be moving to the subscription model, either in LR6 or shortly after that.
Lr upgrades are 80 bucks and adobe seems to be releasing major updates every 12 to 18 months. The photography bundle is 120 a year (or 10 dollars a month). This includes photoshop, so I guess you can make a case that if they do force us to subscription the price isn't horrendously expensive. My concern though is being locked in to the subscription process. I don't always upgrade my software, so why pay for something I'm not using.
I'm rather hesitant to commit to Adobe for this reason. I'm like as an application LR though I'd still consider myself a novice with it.