So I am interested in getting this game but I hear that it gets quite hard pretty quickly so I was wondering if I should get Splosion Man first? Also, is it likely that Splosion Man will be going on sale soon?

You could always do with some more splodin' in your life.

You could always do with some more splodin' in your life.

• Get The Maw first
  
• Followed by Splosion Man
• Watch a 'Lets Play' of Comic Jumper
•  And finally end by perchasing Ms. Splosion Man.

And when I say end, I mean completely disregardThe Gunstringer, because it's a Kinect game.

You should have when they had it on sell for $2. I bought it then, and I can't say I'm crazy about it, but it's not bad.

JasonLeeson knocked it out of the park, by all means follow his suggestion! 
 
but to add my own experience I totally did a marathon run of 'Splosion Man so I could be up to speed with Ms. Splosion Man, I don't regret that decision at all, it is an awesome game. I even could find people online for multiplayer (though those could also be other guys doing a retrospective) 
 
anyways... NICE SPLODING!

I highly recommend getting both. If you enjoy challenging platformers...

I've played through a lot of the Single player now (up to 3-14), and there's one thing that stands out: compared to it's predecessor, Ms. Splosion Man doesn't pull any punches. The difficulty is there right from the start and only ramps up as time goes on. It does feel like it expects you to have played the original, throwing old enemies and mechanics at you with little explanation.
 
The original might be better if you're on the fence, it's still challenging but has a much shallower learning curve.

I've played through a lot of the Single player now (up to 3-14), and there's one thing that stands out: compared to it's predecessor, Ms. Splosion Man doesn't pull any punches. The difficulty is there right from the start and only ramps up as time goes on. It does feel like it expects you to have played the original, throwing old enemies and mechanics at you with little explanation. The original might be better if you're on the fence, it's still challenging but has a much shallower learning curve.