AC voltage rating of ceramic capacitors
For higher frequencies, the voltage rating is decreasing. Can i infer
a similar behaviour for similar ceramic capacitors that do not provide
an AC rating?

Look at the graph; the downwards curvature for all the devices is implying a constant maximum RMS current. It's not exact but it's pretty consistent.
So, look for maximum ripple current rating in a prospective data sheet. That will tell you what the maximum voltage is that you can apply at a given frequency.