It's up to you as you don't know what will happened next.

If you are really eager to buy bitcoin, you can make an entry point on whatever price. If such a case that after you bought your coins then price went down more, that's the time you will face the "risks" we are talking once you enter bitcoin investment. If you eye for long term (since you said you believe it's going to experienced again an uptrend) then just proceed with your goals while taking advantage of that dip. Yes if you have some extras try to ride the downtrend by adding more coins at your stash.