18 “Remember not the former things,
nor consider the things of old.
19 Behold, I am doing a new thing;
now it springs forth, do you not perceive it? (ESV)
Ask yourself, however, whether or not these verses appropriately apply to the deliberate implementation of popular church growth strategies. In your efforts to answer that question, bear in mind that these two verses belong to a larger prophecy. This larger prophecy pointed firstly to Israel's return from the Babylonian Captivity and ultimately to Christ's Second Coming. The two preceding verses look back to God parting the Red Sea, establishing the idea that verses 18-19 promises a deliverance so magnificent and astounding that Israel would "forget" all about the Red Sea miracle.
Notice that the "new thing" that God promised through Isaiah had nothing to do with actions He wanted the Jews to take. He didn't instruct them to abbreviate their sermons, write fun songs that neglected doctrinal content or hold services to appeal to their heathen neighbors. He would do the "new thing," apart from their effort or cooperation.
Isaiah 43:18-19 doesn't endorse changing a church around for the purpose of attracting more members, nor does it sanction change for the sake of change. Rather, it promises that, in His perfect time, God will deliver His people in such a miraculous way that even the parting of the Red Sea will fade from memory. I find that promise thrilling!