Yes you can keep your 4.3 for future but if you ever have to restore it you won't be able to restore it to 4.3 unless you have those SHSH saved. If you are going to jailbreak using greenpoison or something similar it will work fine. Pwnage tool will not work since you will have to restore custom firmware file using itunes. So if you don't have 4.3 shsh restore won't work