Indeed, which is why I don't think they'd even make it that far. Even after Teutoburg, Tiberius launched a series of decisive military actions just five years after under the general who would gain the agomen "Germanicus" for his victories. By 16, the Germanic alliance under Arminius had been devastated, and only the decision of the Emperor not to annex Germanicus' gains prevented a third campaign from coming to pass. The Elbe is not a very good frontier from a Roman perspective; the Rhine, with its origin in Helvetica and breadth of span, was ideal for the purpose of supplying Legion bases along the Limes Germanicus. The Elbe, by contrast, would have required a massive overland trek through woodlands filled with hostile tribes to reach, for extremely questionable gains - the Germanic hinterland was just that, a hinterland with little economic worth. Limited Roman colonization in the area was apparently lackluster and incomplete, as far as I can tell. Raid it, put pliant chiefs in place over the tribes, and maybe nibble a bit around the edges, but a full-scale integration of the entirety of the province into Rome feels a bit difficult. Perhaps, at the largest, I think we might see something that reaches the Weser (with an overland portage being from the Rhine via the Main), but even that might be a bit unstable.
Perhaps the most significant consequence of a victory at Teutoburg would have an extension of that overstretch to eventually be cut off in some Varian defeat, as well as a lack of action to strength the Limes Germanicus into a cohesive fortification chain (since there would be no apparent need to do so) until such a crisis occurs. If they do reach the Weser, they'll almost certainly eventually be forced to regroup on the Rhine-Iller-Danube line again by the third century, due to much the same reason as they did historically - barbarian pressures under a decaying military/state apparatus.