Will 8 decimal places really be feasible in the future?
You need to consider two separate effects:


Mining starts being funded with tx fees rather than inflation. This will result in higher fees, until tx fees per block are similar to current inflation (maybe 1-2 orders of magnitude less).
The value of every bitcoin increases. The real tx fee per transaction remains more or less the same. The nominal fee decreases. The number of txs per block increases, resulting in an equivalent nominal total fee per block. The real total fee per block will increase, to fund greater security for the bigger network.


The 2nd effect is expected to be bigger in magnitude, and to happen sooner, than the first. So overall, we should see a decrease in the nominal fee per tx, allowing us to use small fractions of a bitcoin (which will then have significant value, in real terms).