Recommended bit sizes for a given cipher do increase but only very gradually, since the attack cost is exponential in the number of bits. 20 years ago 1024 or 2048 bit RSA was standard; now 2048 is recommended as a minimum for extremely high-value and long-lived keys (i.e. CA root certificates) but that's all. Host key lengths are actually shorter these days than they were 10 years ago, since algorithmic improvements (elliptic curves) allow the same level of security with much shorter keys.