Date Dec 16th 2017.
Based on the block stats of the few last days, block gas limit being around 8 million, block time little short of 15 sec and the block used gas / gas limit ratio approaching 95 %, the current theoretical transaction cap appears to be around one million (1.0 M) transactions per day.
Apparently the block gas limit was raised somewhere around Dec 4th as the block time and size jerked upwards and block count downwards. The most noteworthy change was the ratio of uncles, which jumped from avg. 12.2% to avg. 26.1% (Byzantium era since Oct 16th). If I've understood correctly, uncles are a nuisance to those whose transactions ended in them, and detrimental to the efficiency as they have to be reprocessed?
We're probably crossing that one million txn/day milestone as I write this, or at least during the very few next days.
To make space for more transactions, the block gas limit should be raised again?
This will either increase the block time, or, if the block time needs to stay at 15 secs, the difficulty must be lowered?
Both longer block time and lower difficulty lead to more uncles?
More uncles deteriorate the efficiency and hence the performance of the blockchain?
Longer block time / lower difficulty also exposes the chain to attacks?
How sensitive is the system for additional increases to block gas limit, and is there any other very short term measures to accommodate the exponentially increasing transaction load?