Extensions these days generally mean nothing except popularity measured by public awareness. Of course there are 'reserved' extensions and many ccTLD's still have not been open to world wide usage (what we call 'liberalised'), but generally extensions are becoming less and less important.
However, your question asked will there be a time when no extensions are needed. If that did occur then only one company could own 'flowers' (as your example) whereas with the liberalisation of the ccTLD's many different companies can own 'flowers.??' or 'flowers.???'. This is one of the major areas for growth in the near future, the uptake by companies of lesser gTLD's and ccTLD's as they realise that they can also own memorable domain names, indeed with the right marketing they can utilise the suffix to their advantage, an example would be 'fish.com' and 'fish.net', it would take little marketing skill to promote 'fish.net' to make it as popular or even moreso than 'fish.com' amoung anglers.
Take away the suffix and you reduce choice and marketing ability and unleash confussion. Embrace the suffix and you can make a leader in the market!