Yes, most current signal boosters are designed to support 5G in addition to 4G LTE. They boost the low-band and mid-band frequencies that carriers are using for both 4G and 5G services. If your booster is approved by the FCC, it will boost the 5G frequencies that are allowed for consumer signal boosters in the U.S.
It’s important to note that not all 5G frequencies are boosted by consumer boosters. For example, the 600 MHz band used by T-Mobile for 5G is not authorized to be boosted by any signal booster. But most 5G services, especially those providing widespread coverage, use frequencies that are supported by multi-carrier boosters. These boosters work seamlessly with both 4G LTE and the 5G frequencies that have been approved for boosting.
When it comes to being future-proof, many of the same low and mid-band frequencies used for 4G LTE are also being used for 5G, meaning that a signal booster you buy today will continue to support those frequencies as carriers expand their networks. Since most carriers are rolling out 5G on existing frequencies, your booster will likely remain useful for years to come.