"that will supposedly" is correct and can be used in written English.
It is used to indicate that something is believed or expected to happen, but there is some doubt or uncertainty about it. Example: "The new movie that will supposedly break box office records is receiving mixed reviews from critics."
Philip poses as a Swedish intelligence agent and recruits her to do spy work that will supposedly help America.
Webb urges strong border security, including the construction of a fence, coupled with strict enforcement of laws that will supposedly stop corporate exploitation of cheap illegal labor.
So, news flash: these programs don't just benefit Those People; they're also very important to downscale whites, the very people that will supposedly rescue the GOP.
By producing a vehicle that will supposedly cost "one lakh" (100,000 rupees or $1,970) he hopes to create a whole new class of road users.
It involves changing the design in ways that will supposedly reduce the chance of death for car drivers colliding with S.U.V.s or trucks by twenty-eight per cent.
Nielsen has embarked on a new private and public campaign to get Democrats to consider legal changes that will supposedly ameliorate the situation.
"Promising to build" is the operative phrase here, because in almost every case the services that will supposedly make these coins valuable have not yet been finished.
And this summer, Hungary has followed suit – starting work on a fence that will supposedly separate it from Serbia, its southern neighbour.
The ease and convenience that will supposedly follow from investing in a new London property is at the heart of much of the marketing material.
Through the joint venture, the two companies are already testing Elations, a drink that will supposedly help ease the aching joints of aging baby boomers.
But the details of such constraints keep vanishing, while ever more of the messy work of coming up with them is assigned to a so-called Medical Advisory Board that will supposedly recommend them later on.
