The news by DEBKAfile that the Russians are discussing Assad’s ouster could be just a way to pressure the Iranians into accepting the truce in Aleppo.
The Iranians have been preparing for a long time to launch a major offensive in Aleppo. They do not want a truce there. But the Russians have agreed to the truce. So now there is disagreement over the truce in Aleppo between the Russians (and Americans) on one side and the Iranians on the other side. The news that the Russians are discussing the ouster of Assad with the Americans can scare the Iranians and pressure them into accepting the truce.
The same applies to the statement today by Sergey Lavrov that “Assad is not an ally of Russia.” This statement does not add anything new to the usual Russian position; but making this statement today is probably meant to pressure Assad and Iran into accepting the truce in Aleppo.