It should be just fine. IIRC, Van's offers a one-time update to the plans, and you should have no trouble keeping up with updates after that. Most plans changes are small and easy to implement even if you have older components. Now, the next question to ask yourself is what if the tail was already assembled? Would you consider it obsolete? I don't think so. I bought my kits from the factory but by the time I got my finishing kit the tail of my RV-6A had been built for over a decade. Things had changed, but not substantially and my airplane flies just fine with its 'old' tail.
The only real issue with an older kit is the condition of the components. But unless they were stored really poorly, it should not be a problem. You'll hear horror stories of the plastic on the parts being hard to remove or corrosion found underneath but a heat gun solves the first and the latter is uncommon and easily inspected for. Don't worry too much about surface corrosion on bar and angle stock if it's light because you can clean and prime the parts you fabricate from those materials. If you have any doubts, have a tech counselor or other builder look it over before you buy it. But being five years old, in itself, is not a show-stopper.
