I see a lot of problems with a 20MB block.
The blockchain database could grow to 1000GB instead of 200GB per year.
Blockchain spam could be a much worse problem.
If the bitcoin decentralized database grows too big it will be more centralized, centralization is a very bad thing.
The blockchain security will be weaker, as the block reward for miners halves, and miners have to depend more and more on mining fees instead of the block reward, by having a 20MB block there will be little motivation to pay any transactions fees at all, causing lots of miners to quit weakening security. With a 1MB block if you are buying something that represents a large amount of money like a car, house, computer, etc you will be motivated to pay a higher fee for a quicker transaction, and for a micro transactions representing something of very little value, it will not be a problem if you have to wait a longer time than usual for a confirmation to confirm the transaction, but on the other hand for a transaction with a tiny value for example a 1 mBTC  if you do not wait for confirmation the risk is little do to the amount.
In the very futuristic event that a block were to be generating more than 25 BTC in rewards based on fees, this would imply a large fee  to get the transaction though in the next block in such an event it could be considered to increase the block size only and only if the current block size would become a problem.

But as things stand now, 1 MB block limit is not a problem, and in the near future it will help secure the network by motivating the miners, only in a very far future it could be needed to be increased, but in such a case then a study would need to take place since in a far future the block reward could be 2 BTC and most of the miners reward could be based on fees as Satoshi had originally planed.

As of today for each block reward, 25 BTC are the block reward, and only on average 0.1 BTC are from fees, the amount of 0.1 BTC would go down to near 0, and that will be a problem for the security of the blockchain once the block reward is something like 3 BTC.

Another thing to consider, today people using modems and low bandwidth can be bitcoin nodes, with a 20MBblock they will need at least moderate bandwidth.

The 20MB block might be needed in the far future but not now.

Also a fork risks the price of bitcoin going down since some may stay on the other side of the fork.

It is better to concentrate on bitcoin gaining adoption instead of solving a problem that today does not exist.