'will have been able' is correct and usable in written English.
This sentence structure is used to express an ability or capacity to do something in the future that has been achieved or acquired at the time of speaking. Example: By next year, I will have been able to save enough money to buy a new car.
Perhaps by then some of them will have been able to come off work experience and get a proper job.
There is no chance that they will have been able to access a European embassy to secure a visa, as none remain open in their country.
On his American tour, for example, Cowdery will have been able to point to the FTSE 100 for evidence that he's a serious player.
It is now likely to be seen in February, by which time No 10 will have been able to gauge public reaction to a tax on sugary drinks.
The incumbent bums, who will have been able to enact the program on which they were elected, can be judged on their record and thrown out (or retained) all at once.
Scientists will continue tracking and looking at the rock over the coming year, after which they will have been able to track its orbit and work out where it lives.
"If Chrysler does recover, then they'll have been able to get that stake at a lower valuation than they would have to pay after an I.P.O".
You'll have been able to do so because of the cultivation of "light-stable hops".
Unfortunately, if drugs are that thing, it's unlikely you'll have been able to do much preparation – those guys driving folded-up lottery tickets door to door tend not to publicise how boric acid-y their cocaine is.
Unfortunately, if drugs are that thing, it's unlikely you'll have been able to do much preparation those guys driving tiny plastic baggies door to door tend not to publicize how boric acid-y their cocaine is.
He predicted that in 20 years, such mechanisms will be thwarted because the land trusts will not have been able to protect the land.
