The end spoken of in all religions is not physical only spiritual. It refers to a new manifestation of God who will bring new teachings and maybe add laws. This is clear in the words spoken above. Light is truth and the world is renewed with each prophet. All religions have seasons. Spring summer autumn winter. Winter is the end. Approx 250 years per season dependent on what is necessary. Gods in charge of that.
The end spoken in BKs is physical though not total annihilation but massive destruction , and we also say that The MahaBharath war is in reality the remembrance of this final war and this would be coupled with many natural calamities which would destroy and drown great regions of the earth.
The analogy of seasons which you mentioned is very good . The four seasons to us in some ways represent the four ages (Satyug ,Tretha, Dwapar and Kalyug), the Golden, Silver , Copper and Iron ages. Spring and summer are bright by themselves and do not require extra light ( guides) , autumn and winter need light and protection.
The first two represent the day of mankind , the root and trunk of the tree where there is unity and strength, and the rest two represent the night of mankind where there is diversity and differences.
And the old leaves of this human tree also fall off before a new spring , though the souls are eternal the bodies have to be shed.
We see each new religion as a new branch in this tree , and each branch has its leaves(followers) hanging on to it. It never happens when a new branch sprouts , leaves from the other branches fall off and cling to this new one . Yes , the fragrance of the new one can spread to others .
Even if for the sake of discussion, I agree that there is a complete spiritual renewal after each Prophet , there are many other corruptions which cannot be settled without the physical renewal of the earth.
1. The pollution of all the elements ,and the emptying of resources, how will only spiritual renewal fix this.?
2. The rate at which our populations are growing , image if we give 1000 more years to the Bahai faith , were would our numbers reach ?, Will this Earth of ours be able to both sustain and accommodate such huge number of people.?