What are the main differences between Traditional Dispensationalism and Progressive Dispensationalism?

Answer 1

Traditional doesn't change; Progressive does.

Answer 2

ARE PROGRESSIVE DISPENSATIONALISTS REALLY 'DISPENSATIONAL?'
Progressive dispensationalists are often accused of not being true 'dispensationalists.' This begs the question – what is a dispensationalist? Is a dispensationalist one who sees a series of 'dispensations' in God's dealings with mankind? Is a dispensationalist one who sees a future tribulation, followed by Christ's second coming to the earth to establish His Millennial Kingdom, with Israel inheriting the land promised her, and being head of the nations? Is a dispensationalist one who interprets Scripture literally? If these are what characterize dispensational beliefs, then surely progressive dispensationalists are true 'dispensationalists,' since we firmly hold to all of these things. Progressive dispensationalists therefore cannot rightly be charged with "replacement theology" – the belief that God is finished with Israel, and the Church has usurped all of the promises at Israel's expense.

DISTINCTIVES OF PROGRESSIVE DISPENSATIONALISM
Progressive Dispensationalists see a progression of dispensational economies in a single unfolding plan to redeem mankind. We acknowledge only one means of salvation for all time, by grace through faith. The effect of the sacrifice of Christ was retroactive for the Old Testament saints who died in faith [Heb. 9:15], "that they should not be made perfect apart from us." [Heb. 11:40]. It was God's original purpose "that in the dispensation of the fullness of the times He might gather together in one all things in Christ, both which are in heaven and which are on earth-- in Him., [Eph. 1:10]. Paul was referring to an already accomplished union of Old Testament and New Testament saints. "For this reason I bow my knees to the Father of our Lord Jesus Christ, from whom the whole family in heaven and earth is named." [Eph. 3:14,15].

THE PRIMARY DIFFERENCE - 'PARENTHESIS' vs. 'PROGRESSION'
Traditional dispensationalists typically see the 'church age' as an interruption or parenthetical period in God's dealing with Israel. The church is seen as unrelated to Israel and the new covenant promised in Jeremiah 31:31-34. Believers of this dispensation are segregated from believers of other dispensations in purpose and destiny. Consequently, they see the new covenant as entirely future, concerning Israel during the Millennium. This segregation of saints is best seen in the concept of the 'Church' being exclusively the Bride of Christ to the exclusion of other saints. Progressive dispensationalists however believe the 'church age' is the fulfillment of certain promises in the Old Testament, regarding the new covenant, and salvation of Gentiles. Rather than being unrelated to God's program for Israel, the Church is an integral part of that program, and is currently participating in the new covenant promises in this dispensation. Progressive dispensationalists believe the New Covenant was inaugurated by Jesus Himself, by shedding His blood, [Luke 22:20, Heb. 8:6, Heb. 9:15]. Jeremiah prophesied the New Covenant would be made with Israel [Jer. 31:31-34]. A look at the Gospels shows the 'good news' was originally presented to Israel exclusively. In fact, when Jesus sent His disciples out to preach the gospel the first time He explicitly told them not to preach to Gentiles [Matt. 10:5,6]. Later we find Paul's acknowledgment of this fact with the words, "to the Jew first, and also to the Greek" [Rom. 1:16, 2:9,10]. The crucial difference can be summed up as whether the Church is the fulfillment of Old Testament prophecy, and whether saints of various dispensations should be seen as segregated.