I should bookmark the page from Reusch's web site. He says it is difficult to control the products and product ratio in an SN1/E1 reaction. I have yet to find anything more accurate.
I expect a mixture. If heated, it will increase elimination. However, HBr is the by-product. I expect it would catalyze protonation of the alkene and catalyze ether formation. The alkene is less basic than the alcohol, so this reaction may be slow. Not only that, but the HBr will also protonate the ether and drive it back toward the alkene. I still say mixture.
A very common ocher lab experiment is the solvolysis of t-butyl halides. I too wondered what the products of this reaction should be. I failed to find a report of the products. I suspect the ratios of alcohol and alkene vary from reaction to reaction.