I would have definitely invested in Bitcoin back when it was at roughly $400, but right now isn't the time.
Buying bitcoins after 4 years will not be easy as it is at a moment, this is the price that we can still afford to buy but when it crosses 4 digits price it will be really difficult to invest money in it.
If you want to do your buying, then do it right now instead of after a few years as the price by that time will be much higher.
If we are a long term holder and if don't buy now then we will surely regret in future as price would be definitely higher at that time, so I think if you have faith in bitcoin then this is the best time to buy.