No, they weren't on an upward spiral, at least not in terms of power relative to their neighbors. Macedon made the error of allying themselves with Carthage during the Punic Wars to acquire Roman territory in Illyria.
The Romans, while concentrating on Carthage for the moment, actively set about undermining and subverting Macedonian rule in the former Greek city-states, and were highly successful. The Romans thus had a toehold in Greece, and were welcomed by the Greek poleis as liberating them from Macedonian rule. Only after it was too late did the Greeks realize that not only did Rome seek the conquest of Macedon, they weren't leaving Greece either.
The Romans had been content to let the Greeks govern themselves under Roman rule, but the Greeks rebelled. Rome completely destroyed Corinth in 146BC to set an example, in the fashion of Carthage. A revolt in 88BC was met with severe suppression, many Greeks were slaughtered, looted, sold into slavery, etc.
The days of Alexander's Empire were long over, with it being divided under the Antigonids, Seleuicids, and Ptolemiacs for some time. Each of these successor dynasties slowly declined over time, and outsiders such as the Romans could easily employ such strategies as divide-and-conquer.