DSLRs are stupid cheep, dude. I paid $1800 for a used Nikon F5 in 2002. Y'all get off so easy these days.

Look at it this way: a camera is nothing more than a box with a hole in it. You can control how long that hole stays open, how big it is, and what's in front of it. That's it. When you aren't using an SLR, you're giving up control over the first two of those three parameters. Your P510 gives you a lot more control than an iPhone but whenever I see "43x zoom" I know I'm looking at shitty glass. Nice thing about an SLR? You can trade in your shitty glass.

Tell you what: buy this book. Look it over and see how many of the techniques within it can be accomplished with your P510. Do those. Then when you've beaten your camera into the ground, get a better one.

I shot a Nikon N70 for two years until the shit it couldn't do was boning me. Then I moved up to the F5 until I found its limits. Then I shot a Pentax 6x7 until the whole fucking world forgot how to develop slide film and I had to stop taking pictures for like five years. Then I bought a Canon 5D for craptacular amounts of money and it's been serving me well for like 10 years 'cuz I got good glass. Eventually I'll upgrade to something better but "something better" is now like $10k rather than $2k so I'm not in a hurry.

If what you got isn't holding you back yet, there's no reason to upgrade. There is, however, ample reason to push past your limits.