Chief Officer Wilde was only to be on this maiden voyage and when Olympic was back to shape and the coal strike was over, it appeared that David Blair would resume his position on Titanic. White Star thought it would "look good" if Officer Wilde was present on the maiden voyage due to his experience on Olympic.
This is only an "assumption" of course because we will never really know what would have transpired unless Titanic would have made her trip to New York and back.
I assume you've read his entry in these pages, which mentions that he was on the Titanic's sister ship, Oceanic, in September 1914 when it sank (!!!). Your question specifically asks what his NEXT assignment was, but wouldn't Oceanic have been the logical choice, since weren't some of Oceanic's crew transferred to the Titanic, thus creating vacancies? Also, where else could he have been assigned to, as a White Star employee?
Some of the details of his adventures on the Oceanic (he was court-martialed after her loss) are on this link:
I have a small bit of info on Blair. He was born on November 11, 1874 in Newport, Isle of Wight. In 1896, having failed an exam for his second mate's "ticket" months earlier, Blair wrote to the "Examiner of Master and Mates-Dundee" for permission to retake his exam. His three month wait to retake the exam was not yet up, he explained in his cramped script. He was granted permission and passed his exam, for which he was awarded a second mate's certificate or "ticket".