So much depends on what level of "Pro" you are moving towards. "A few jobs with the K-50" is what I would call "borderline professional". I'd say, at that level, and maybe a few more up-ticks, you will be fine staying with Pentax.
If the work you are moving towards, is global, 24x7 and at a moments notice, shooting and filming whatever is asked for, then I would say no, Pentax is not a viable choice.
The eco-system that surrounds Pentax is not enough to sustain integration with other professionals, and cross platform hardware makes for a difficult workflow. Professional workflows are based on efficiency and throughput, and Pentax is niche.
The quality is there from Pentax, sure, but the market dictates the professional workflow.
What am I talking about?
Here is a scenario...and a real one.
"Lauren, I hear you are coming to the UK. We are going to film a music video, at Lyme Regis. You in? We'd like to use your drone and maybe have you pick up a few other shots along the way. Would you be up for some directing too?"
I agree, and I'm off to the UK.
The other folks on the team, shoot with A7SII cameras, and an FS700. There might be some Osmo in there, and of course our drone shots. For stills, we will have the A7SII cameras, which will be recording 4K on Atomos devices, installed on some Ronins. Since the A7SII cameras are also FF, they can duplicate any other FF stills camera that is out there. Everyone knows how all this hardware works, so there are no guesstimates, and an efficient workflow results.
Sure, I have my K1 with me on this shoot, but because it's the "odd camera", it might make it into the professional workflow, but probably not. Therefore taking it, is a personal choice only. In a professional setting, there is no way I am going to "introduce" people to Pentax. There are no technical features that make the K1 a "go-to" in many workflows. The K1 is a great camera, but Pentax hasn't put anything into the camera that would make it a must have on a shoot like this.
The one thing...is that Pentax cameras are weather-sealed, and in this shoot it was raining and windy. If Pentax would have just given the K1 a decent video codec, and a flat profile, and at least 1080p/60, the K1 *could* have been included.
Alas, another opportunity missed.
The below music video brought to you by a Pentax shooter on a team using Sony and DJI equipment.
Enjoy.