HBC will survive an official 4.3 update, but u never know when ninty will put out 4.4 update, and who knows what anti-homebrew they have in their next update
also, updating officially to 4.3 will stub your cIOS249 and remove bootmii @ boot2 if installed and if its below v4
performing an official update is pointless when u can just use ModMii to update without stubbing cIOS249 and overwriting bootmii. But if u were to update officially, u can always rehack it. If u still have the HBC after the update, u can do so without needing a disc based exploit.
anyways, the rule of thumb is, if ur wii is softmodded, don't do an official update, u never know what surprises they could have in store for u... and trust me, u don't want to be the first one to report "4.4 update removed all my softmods!"