Yesterday as Mass, after receiving Holy Communion, the celebrant ended Mass...No blessing, No "Thanks be to God" etc. He said we have a new practice ending Mass and we will end with a song of giving...is this acceptable?

No. The correct form for the conclusion of Mass follows.

Regarding the conclusion of Mass, the Sacramentary provides the following instructions:

Concluding Rite

If there are any brief announcements, they are made at this time.

Greeting

The rite of dismissal takes place.

Facing the people, the priest extends his hands and sings or says:
The Lord be with you.
The people answer:
And also with you.

Blessing

A. Simple form
The priest blesses the people with these words:
May almighty God bless you, the Father, and the Son, and the Holy Spirit.
The people answer:
Amen.

B. Solemn blessing
Texts of all the solemn blessings are given on pages 569-579.
Deacon:
Bow your heads and pray for God's blessing.
The priest always concludes the solemn blessing by adding:
May almighty God bless you, the Father, and the Son, and the Holy Spirit.
The people answer:
Amen.

C. Prayer over the people
Texts of all prayers over the people are given on pages 581-585.
After the prayer over the people, the priest always adds:
And may the blessing of almighty God, the Father, and the Son, and the Holy Spirit, come upon you and remain with you for ever.
The people answer:
Amen.

Dismissal

The dismissal sends each member of the congregation to do good works, praising and blessing the Lord.

The deacon (or the priest), with hands joined, sings or says:
A. Go in the peace of Christ.
B. The Mass is ended, go in peace.
C. Go in peace to love and serve the Lord.
The people answer:
Thanks be to God.

The priest kissed the altar as at the beginning. Then he makes the customary reverence with the ministers and leaves.