Yes, there are some downsides to RISC processors. For one, as I mentioned earlier, certain tasks (like floating point operations or division) can't be performed with a single instruction except in some of the newer RISC designs.
So even if a single instruction runs faster on a RISC processor than the same instruction on a CISC processor, it may take dozens of instructions to perform some operations that a CISC processor can do with a single instruction.
And there is a double-edged-sword with RISC technology. The companies that develop the designs don't actually manufacture the chips – they license the technology (referred to as cores – reusable, and sometimes customizable, blocks of logic or chip layout designs) to other corporations.
And like any good department store would do, they lower the licensing fees on older versions of the design. So if a manufacturer wants to use the latest and greatest version of a RISC design, they pay a premium, but if they don't need the latest and greatest features for a particular application they can license an older version. Nearly every RISC architecture design ever developed is still available if you want it.