Are the cpu speeds that we enjoy today a bubble?
No but you could say the speed increase we've enjoyed over the past decades will hit a brick wall. In so far it hasnt already. And moore's law is running out of steam too. IIRC on some chips we are down to feature sizes that are just a dozen atoms wide, transistor size is approaching atomic levels. It just doesnt get smaller than that. We are not there yet, still a few shrinks that are probably feasible but the end is in sight.
Moore's law itself does scale further, though there is walls with gains and prices.
You just need to add more chips for Moore's law to work. Though this is costly and gains aren't very good beyond some point.