Question About New Coins Taking Over The Previous Design Coin.

Plently likely. Those of us who were around in the early 1960s can tell you they were still in circulation then. As were Standing Liberty quarters (not as often) and Walking Liberty halves (very common).

What would really have been a trick worthy of Twilight Zone would be to see Roosevelt dimes in 1934

Even in the early 70s you could find a Mercury if you handled change. SLQs typically were dateless (I have a roll put together from circulation and none have a date). Franklins and WLHs were not too hard to find if you went to the bank and got a a hundred dollars or so in rolls. People did not hoard it as much though b/c the value was not worth their time to "go all out." It was more just a fun thing to find that "would be worth something some day."

It depends on a lot of factors, but in the end, people hoard what they perceive as being inherently more valuable.

I was born in 1989; every denomination except the dime has been redesigned at least on one side since I started collecting in the late 90s. With the sole exception of 2009, none of them are "worth" more than face value, and coins going back to the 60s are common in circulation.

The big collecting fad of the 50s/60s helped drive the wheat cents and older denominations from circulation; from responses here in the past, wheat cents were uncommon by the early/mid 70s, and "special" by the 80s, despite the fact that they still exist by the billions today. The perception of an extant market has led to an actual market, which drives coins from circulation.

Now how long will it take for people to perceive memorial cents, pre-2004 nickels, and pre-1999 quarters as worth saving? Anyone's guess, but I'd give them a couple more decades at least.