"should be joining" is correct and can be used in written English when discussing an action that someone should take.
For example, "She should be joining us for dinner tonight."
Republicans and Democrats should be joining forces in taking this important step.
"In the next couple of weeks I should be joining in with the lads.
I think Drogba should be joining us, if all goes well, but that is not my position to announce".
Their next step should be joining forces to maximize opposition strength and help assure the dictatorship's defeat.
"The senator who is connected to these folks should be joining me in asking for these resignations," Mr. Manganello said in an interview yesterday.
Hodgson was more positive than Appleton's chairman at Blackpool, Karl Oyston, who spluttered his disbelief that the 37-year-old should be joining what he described as a "disaster shipwreck".
They should be joined up".
Battle royal should be joined over its amendment.
They should be joined in the upper echelons by their Yorkshire neighbours Bradford City.
Another says: "The causes of poverty are interconnected, so the solutions should be joined up too: health, education, housing, justice".
Universities UK has previously argued that Offa should be joined with Hefce, and it is also potentially in scope for the BIS review.
