As discussions on previous pages indicated, linear increase in block size may cause the effective bandwidth in the network to grow exponentially due to peers sending the same data to to each other many times. So it's not 1MB per every 10 minutes, the actual bandwidth is much higher.
Bitcoin does not use a stupid block propagation algorithm, such as would be needed to create exponential overhead. It may have overhead that is constant in node connectivity, whereby a node receives the same block from each of its neighbors. However, if so, this is easily fixed by flooding the small block header to each neighbor once, but having neighbors request the block data from only one neighbor. In this case, each node receives only one copy of each block. (Well connected nodes with many fast connections, may send multiple copies to many less connected nodes, but poorly connected nodes will send few copies, with the number of "takeoffs" being equal to the number of "landings".) There is the opportunity for fine tuning the request process, so that nodes request data from new blocks from those neighbors that are known to have a fast ability to send them. There may be some small overhead related to the discovery process. (These kinds of issues exist in other peer to peer networks such as bittorrent and have been solved.)
I've been thinking in the same direction.
I mean, it doesn't have to be exponential.
If every full node receives each transaction only once(?), then there was a proposal to only send a block template and let each node reconstruct the actual block from the list of transactions and the data it already has in its memory pool. A node would then only need to request missing transactions (if any) from other peers.
I don't know if that was implemented or not, but a good implementation would likely approximate a linear bandwidth increase (relative to block size cap increase). Still, I wouldn't aim much higher (than 8MB) for the time being simply because those solutions need to be deployed first and even then we need to make sure that different parts of the world can join the network easily in order to keep the whole system properly balanced.