If the Constitution did not contain the Copyright Clause, would Congress still be able to implement copyright under the Commerce Clause or another part of the Constitution? Assume that the Constitution never contained the Copyright Clause, rather than the clause being repealed.
Eventually. This was a state matter prior to the enactment of the Constitution. Without the Copyright Clause, it would have been up to each state to enact such a law (apparently Delaware did not bother). This would have quickly led to inter-state disputes (a New York author being infringed by a New Jersey party), therefore the matter would have been heard by the federal courts.
The current understanding of the Commerce Clause easily allows Congress to enact a copyright law, because copyright is quite commercial and potentially crosses state lines. It took a while for that clause to be interpreted by the courts the way it is now. This is a brief summary of historically shifting views on the Commerce Clause.