Former Ireland paceman Rankin is hoping to make his England one-day international debut in the RSA Challenge against his old team-mates in Dublin.
Rankin made 37 appearances in the 50-over format for Ireland, and featured in their stunning defeat of England in the 2011 World Cup, but switched his allegiance to further his career.
The 29-year-old has impressed selectors with his performances for Warwickshire and the England Lions and Morgan believes he is ready to make the next step up.
Morgan, whose own change of country has brought him 16 Test caps, said: "Boyd has been involved in our Lions set-up for a little while now and has obviously been part of the international set-up this summer, which is great to see.
"He is bowling particularly well and it is exciting to see him with three lions on his chest.
"The opportunity is endless and if he achieves his potential, hopefully we will see him in a white shirt sooner rather than later.
"I think he has always progressed at his own pace. In the past he has struggled with injury but in the last couple of years he has strung together some fantastic seasons and some great spells of bowling."
Morgan himself has dropped out of the Test reckoning, having not appeared since the series against Pakistan in Dubai in February last year.
He remains hopeful of a recall and feels it helps that he is a regular member of the one-day team.
The 26-year-old is captaining for this autumn's 50-over international programme as regular skipper Alastair Cook is rested.
He said: "There is no doubt I want to continue to try to break back into the Test team.
"It is just weight of runs and lack of form has led me to where I am, being dropped.
"I think one-day runs can help. It was the prime reason I got selected in the first place."
Another Irishman, Morgan's fellow Dubliner Ed Joyce, is now back in his home country's fold after being discarded by England.
Morgan says there is little chance of him ever representing his homeland again.
He said: "No, simply because I think I am 26 years old and you can play Test cricket until you are 35 or 36, if you are very good.
"The opportunity is still going to be there. If you go the Ed Joyce route, that opportunity isn't there."