In a discussion about transaction fee, I just sorted out these facts:
A smart mining pool will calculate the block orphan risk when including transactions (more transactions will raise the orphan rate due to longer broadcasting time)
For example, if a full 1MB block containing 2000 transactions will broadcast slower than an empty block, thus raise the block orphan rate by 1%, then the pool will lose 1% of the block reward, which is 0.25 BTC, divided by 2000 transactions, you get 0.000125 btc per transaction, that's the recommended fee right now
For 2MB blocks, the broadcasting time of such a large block might affect the orphan rate more significantly, say raise the block orphan rate to 4%, and then you can include 4000 transactions in each block. As a result, although each block can hold double amount of transactions, a full block will cost 4x more for miners, so the fee for each transaction would double at 2 MB full block
Currently, due to the block reward, you can not enforce a higher fee for miners, since the miners on today's fast network have very low orphan rate if they include all the 2000 transactions, thus any fee above 0.0001 is good enough for them to happily include it
However, if block is larger and the transactions processing speed (CPU/network) is limited, miners can not include as many as possible transactions without added orphan cost, then I guess the fee will rise when blocks grow beyond certain size, regardless of the block size limit
Only a speed increase in CPU/network infrastructure would lower these cost, and we know that the improvement in those area (especially the fiber network infrastructure) are not that easy to upgrade
The block propagation still depend on location and the time for the block to fully propagate (and thus be safe) depend from where it start. So needing better hardware to compute it faster is one thing, but just getting better hardware will not fully solve that.
So the price would go up per tx as well, yes.
