Backup Plan? Replace OSX but still go back if neccessary?

[bornagainpenguin]

After seeing what the new release of OSX looks like (butt-ugly IMHO, they've now removed just about everything I liked) I'm no longer as adamant about being able to dual boot as I once was. Given the difficulties I had in merely making an SD Card version of Ubuntu bootable with reFit (reFind) I kept putting that on hold any way. Now given the new ugliness and knowing that the older version of the system will be very quickly obsoleted especially given that the last two releases are free I don't expect being able to put off the 'upgrade' for long. I'll miss Facetime but I use Skype more and more often any way these days and last I check that at least was crossplatform.

But...if I discover an app I absolutely need to run, which is OSX only--is there a way back? Can I somehow preserve the ability to do an Internet restore? Is there a way back?

EDIT:

Current Macbook is running 10.9.5 on a Macbook Pro MacBookPro8,1 from early 2011 on a SSD and with 16GB of RAM.

[MikeBraxner]

Personally, I just installed OS X onto an external USB 3 drive, and made sure to copy the installation dmg onto it as well. When I decide to finally sell my mac hardware, I simply boot from the drive, and run the dmg for a clean installation ... easy peasy. As an added benefit, should I reeeeaaallllyyyy feel that I have to use a program under OS X, I can always just boot it up, and run it from the usb ... surprisingly enough, this isn't as slow I would have expected.

[PartisanEntity]

I did something similar to MikeBraxner. I copied my OSX install to an external USB HDD (using Carbon Copy Cloner). My iMac is running on Ubuntu solely.

From time to time I will boot the computer from that external OSX USB HDD in order to install updates, and make sure I have a fall-back system that is up to date in case I ever need it.

IMHO that would be the best approach.