If one Satoshi would be 1 dolar, then the full market cap of Bitcoin would be all the coins available multiplied by it's price.
There is 16707388 bitcoins in circulation at 29th/november/2017.
A satoshi is smallest amount, the one 0.00000001 BTC.
So, if one bicoin is 10^8 satoshis and you suppose one satoshi will reach one dolar, then you really mean is that bitcoin price is will soon reach 10^8 dolars. If you really think bitcoins will be priced at 100 million. So, the total market price would be 16707388 * 10000000 = 16707388*10^8 =~ 16,7*10^14. That is a very great number. 1670 trillion dolars. This site tries to especulate on the total number of money available here.
So, there is still much room for Bitcoins to apreciate before such problem happens.
First, if a satoshi becomes a dolar, there is still much transactions that can be done in a block. A block should have sufficient size to offer many transactions and still be profitable. And if bitcoin apreciates beyond imagination, then people would not use it for small trades. As simple as that. I just don't see people carring diamonds and gold to buy grocery goods.