I totally agree with Adam's response. I'd like to add, if you go pro, there are a few more things to consider:
a) Although Reuters is now requiring photo submissions to only be jpeg, 95% of all pros shoot RAW, convert to DNG, and then have developed enough skill on Lightroom or Photoshop to get the most of the image file (without going too far). This is the final step in the entire process and cannot be overlooked when evaluating what or why are some results better than others.
b) Depending on the field/genre that you wish to go pro, beware that some agencies, clients, and others you'll need to network with are more than likely biased to one brand or another.
Right now, Canon is the flavor of the decade. Old school tends to favor and respect Nikon. When I was a pro shooter, I started with Minolta and Pentax SLRs, but I got tired of fighting the bias against me and found I could get more jobs and better paid with Nikon (back in the '80s and '90s) in Hollywood. In the 60's, if you were a war photographer, you had to have a Nikon F2. A decade earlier and all the photojournalists had Leica rangefinders. I have a young colleague that produces gorgeous Mamiya 645 wedding photos, but she finally gave in because 90% in that industry shoots Canon 5D Mark III (circa 2012). Same with an ex-student of mine that is now a top surf photographer.
Yes, there will be, and one would only hope, clients, agencies, etc, that could care less what you shoot as long as they love your results. But you should do your homework to see if there is a bias in the type of pro photography work you want to get into. If there isn't, then you just need to up your glass to DA* or Limited primes and only the best zooms. Here's a site that can help determine what lenses are getting what results with specific cameras:
DxOMark by DxO - DxOMark
And I'd even suggest considering the K3II. On pro level cameras, you won't find a pop-up flash. A pro will almost always use external flash units or available light. Pentax took a big gamble in not including the built-in flash with the K3II, and I am sure they didn't remove it to save money. Also you'll want to budget or invest in a high end Pentax flash units like the AF540FGZ II Flash.