Ironically, this notion had been floated as early as the Secession Winter of 1860/1, by, of all people, Andrew Johnson.
According to Stampp[1], in a speech in Delaware on Dec 19, Johnson argued that a disloyal State would revert to the condition of a Territory.
Practically speaking, though, the question had little significance. Postwar, even the Radicals were mostly keen to get the South readmitted asap, so that reconstruction (on their terms) would be a fait accompli before the 1868 election campaign got under way. They were eager to ram Black suffrage through before Northern opinion (which mostly varied from unenthusiastic to downright hostile) had a chance to harden against it
[1] And the War Came, Ch 3.