in the next 20 years I might only be able to collect up to 100-200 bitcoin. so I will hold 100-200 bitcoin to see the price $10,000 in 20 years to come
Bitcoin might have failed by then... or maybe the fiat economy will have and 1btc will be worth thousands

. I think 100 bitcoins would be a nice amount to have and hold, though. I think bitcoin will hopefully go back to 1k again at some point and depending on where you live 100k could make your life very comfortable. I know I could survive off that for probably 50 years if you only have to pay rent and food etc. Pesonally I wouldnt set myself goals and just keep a nice amount in btc but one you could afford to lose as nothing is certain.
Bitcoins wouldn't fail in the next 20 years but it would be replaced by another virtual currency similar to other rewards given by banks and websites while shopping. If bitcoins still exist, 10 bTC also would be enough as an investment as now itself the price is about $400 and the price would most probably rise in future as there are very coins left to mine and in 1 year almost all coins would be mined making the price stable.